Re: [grub] Experiencing difficulties to access USB key files

[Andrei Borzenkov]

21.01.2016 14:52, Arbiel (gmx) пишет:
> Hi
> 
> I have written a grub file for booting from PCs which do not provide a
> "from USB key" booting.
> 
> The USB keys to be used are supposed to be msdos compatible (not GPT),
> grub has to have been installed in their first sectors as usual, and the
> USB keys are supposed to contain a grub configuration file (a
> traditional grub.cfg file) and an additional file of which the relative
> path (the result of grub-mkrelpath) is unique in the configuration.
> 
> My grub file searches for the unique relative path to set the target
> device where the to-be-configfiled file lies and I "configfile" it. I've
> released my file to a community forum. I instructed the potential users
> to source my file in their booting grub.cfg file. It works for several
> members of the forum, who are happy with it.
> 
> However, it does not work for a user. We have investigated the situation
> and got some results :

Unfortunately you forgot to describe what happens in case it does not work.

> 1) his USB key is seen by grub as a floppy disk ; the ls command lists
> it as (fd1) ; so I suppressed --no-floppy from the search command
> parameters. To no avail.

How do you know it is this USB stick? What "ls -l" shows? Can you read
something from it (hexdump command)? Can you read enough to identify it?

> 2) as I was not sure of the contains of the original grub.cfg file (the
> one which sources my file), I added a "insmod fat" command, as the
> partition of the key is FAT32. Still to no avail.

Not sure I got it. So GRUB is installed somewhere else? So may be it is
simply too old GRUB version?

> 3) supposing the BIOS was lacking USB drivers,

This directly contradicts 1.

> I inserted five
> additional modules : usb, ahci, ehci, ohci and uhci. No avail.
>

This just makes things worse by cutting off access to $prefix.


> I am now short of any additional idea to make it work.
> 
> Thanks to any of you who will provide me with advice.
> 
> Arbiel
> 
> 
> 
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